Eficiência da seleção para qualidade da fibra do algodoeiro (Gossypium hirsutum)
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2018-11-29
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Universidade Federal de Goiás
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Cotton fiber is the main feedstock used in the world textile industry. It is determined by several traits of complex inheritance, influenced by the environment, and which can be negatively correlated with each other, hindering genetic gains in selection for fiber quality. The aims of this study were to estimate genetic parameters for traits related to cotton fiber quality; propose a graphical method to measure the gain with the selection using different intensities of selection; and to verify the viability of SCI and CSP as selection indices for fiber quality. From the cross between the cotton cultivars BRS 336, conventional with high quality fiber, and DP 164 B2RF, transgenic with medium quality fiber, two populations were carried out: one using the bulk breeding method, and another from the backcross with the cultivar BRS 336. Fiber samples of F5:6 (bulk) and F3:4RC3 (backcross) progenies were analyzed using HVI apparatus, which evaluates the fiber quality by measuring the traits length (C), maturity (MAT), uniformity (U), micronaire (MIC), elongation (ELG), short fiber index (FC), resistance (R), degree of yellowing (b), the spin-consistency index (SCI) and the reliability index (CSP). Genetic variability was observed among progenies for R, MIC, ELG, C and FC, confirming the complexity of these traits. The means of the two populations
met the needs of the industry, indicating the presence of genotypes with commercial potential. Estimates of heritability ranged from 3.29% (Rb - F5:6) to 59.92% (C - F3:4RC3). All traits showed genetic correlations with at least one trait, and negative correlation was observed between C and the traits PF, MIC, MAT and FC. The CSI index presented a negative correlation with FP, MAT and FC, and positive correlation with C and R. The SCI index showed a negative correlation with MIC and MAT, and a positive correlation with C. The selection of the 20% best progenies using both indices presented favorable responses for C, R and FC, with expected reduction in FP, and without significant influence on the other traits. The graphs of the correlated response were more informative than the estimates obtained through the equation, since they do not need the values of genetic correlation, and allow the analysis considering several intensities of selection. The graphs of heritability showed that the selection gains were reduced or negative for some traits as the
selection intensity increased. The strategy of using the gain graphs using different intensities of selection is efficient and easy to be implemented by breeding programs, especially when the objective of the program is to evaluate complex traits, influenced by other characters, such as cotton fiber quality.
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ALVARENGA, L. G. S. Eficiência da seleção para qualidade da fibra do algodoeiro (Gossypium hirsutum). 2018. 65 f. Dissertação (Mestrado em Genética e Melhoramento de Plantas) - Universidade Federal de Goiás, Goiânia, 2018.